Alloy



Patented June 23, 1936 ALLOY Roy E. Paine, Oakland, Calif., assignor, bymesne assignments, ,to Magnesium Development Corporation, a corporationof Delaware No Drawing. Original application October 4,

1933, Serial No. 692,135. Divided and this application-November 15,1935, Serial No. 49,967

2 Clai s. .(Cl.75168) The invention relatestomagnesium-base alloys,preferred casting alloys are those contamm and is directed to thedevelopment of alloys .of this class which have good corrosionresistance,

particularly in the cast and in the cast and heat promise must quitefrequently .be made in order to approach in one alloy the'optimumproperties for a given application. For example, it maybe found thatcorrosion resistance can be sacrificedso to acertain extent to obtainhigher tensile strength, yield point,,hardness, or similar mechanicalproperties. Again, tensile strength may be sacrificed in order to obtainproper casting.

or working characteristics. It is an object of the present invention todevelop magnesium alloys to improvement by heat treatment and -adapt--vision of magnesium-base alloys characterized by,

'good corrosion resistance in either the cast. or in the cast and heattreated condition. A further object is the provision of magnesium alloyspos- I I have discovered that magnesium-base alloys containing from 0.5per cent. to 22 per cent of lead possess to an appreciable degree thecollective characteristicsof alloys which are re sistant to corrosion,alloys which may be readily cast,- alloys which are susceptible" toalteration of properties by thermal treatments, alloys having favorablemechanical properties, and alloys which, within a restricted range, maybe worked by extrusion, forging, or other means of mechanicaldeformation. I

In accordance with my invention leadmay be present in amounts as low as0.5 per cent.- The above about 5 per cent oi lead since it is in thesealloys that the most pronounced combination of these differentproperties is obtained. The alloy may be worked by extrusion over arange offrom about 0.5 per cent to about 22.0 per cent. 'oilead. As anall around casting alloy I have found amagnesium alloy containing 5 to10 per cent of lead to be particularly adapted to general foundrypurposes. Alloys falling within this preferred range of'co'mposition aswell as other alloys comprised within the broader limits previouslydefined, have been subjected to severe tests designed to produceaccelerated corrosion. -Sand cast test bars poured in accordance"with'the best casting practice in the art were subjected to cor-' rosiontests in the as cast and in the heat treated condition. In the examplereferred to the heat treatment was carried out at about 459 centigradefor about 20 hours followed by quenching in'water, and both heat treatedand unheat treated test bars were subjected to that corrosion test whichP T T prince comprises alternatelyimmersing the metal in,

and removingit from, a 3 per cent sodium chloride solution for about'80h0urs,"a treatment referred to hereinafter as the alternate immersiontreatment.

There are certain elements which may be added to the binarymagnesium-lead alloys to particular advantage. Such, for instance,- arethe .metals calcium, cadmium and zinc. These may be added singly or incombination with each other, the zinc in amounts between about 1.0 percent and 10.0 percent, the calcium between about -0.1 per cent and 2.0"per cent, and the cadmium between about 1.0 per cent and 10.0.per cent.

These alloying elements are. substantial equiva-:

lents as indicated by their susceptibility to' thermal treatment inmagnesium l'ead alloys- The calcium fayorably affects 'the castingproperties of the alloy without markedlydecreasing its, corrosionresistanceH'Forinstance, a magnesium alloy containing 21.4 per "cent ofleadand 0.25 per cent'of calcium shows, in the as cast con-' dition,' astrength loss of only 17 per cent afteralternate' immersion in a 3percent sodium chloridesolution for about v80 hourspwhile a heat'treated magnesium alloy containing about 5 per cent of lead towhichabout 0.25 per cent] of calcium had been added did not undergo anycadmium had in thesand cast condition a tensile strength of about 24,650pounds per square inch and an elongation of about 9.8 per cent in 2inches. After a heat treatment of about 20 hours at about 450 centigradeits tensile strength had increased to about 25,140 pounds per squareinch and its elongation to 10.3 per cent in 2 inches.

' of lead; and about 5.0 per cent of cadmium. An

alloy of magnesium with about 5.0 per cent of lead and 5.0 per cent ofzinc had in the sand cast condition a tensile strength of about 23,370pounds per square inch. After. a thermal treatment of about 20 hours at450 centigrade followed by an aging treatment of about 20 hours at 150centigrade its strength had increased to about 25,710 pounds per squareinch. After an alternate immersion corrosion test of 80 hours the lossin strength was only 12 per cent. Another alloy of magnesium with about5.2 per cent of lead and 3.2 per cent of zinc under similar conditionslost only about 10 per cent after 80 hours alternate immersion inthecorrosive solution. As a preferred composition for alloys of this natureI advise 1) 5.0 per cent lead, 10 per cent calcium, balance magnesium;(2) 5.0 per cent lead, 5.0 per cent cadmium, balance magnesium; (3) 5.0per cent lead, 5.0 per cent zinc, balance magnesium. If more than one ofthe elements calcium, cadmium, or zinc be present simultaneously, Iprefer not to exceed a total of nesium-lead alloys and are substantiallyequivalent in this respect that they materially refine the grainstructure of the'alloy. Aluminum, for instance, can be added over a widerange, such as between 1.0 and 15.0 per cent; silicon may be eflectivelypresent forthis purpose in amounts of about 0.1 to 2.0 per cent. ,Whenused in combination it is advisable that the total content 'of aluminumand silicon does not exceed 15.0 per cent. In the preferred practice ofmy invention I have found that the best results are usually obtainedwhen the aluminum is present in amounts U between 5 and 10 per cent.

As a preferred magnesium-lead-silicon composition I use a magnesiumbasealloy containing 7.0 per cent of lead and 0.5 per cent of silicon. As apreferred magnesium-lead-aluminum alloy- I use a magnesium-base alloycontaining 7.0 per cent of lead and 5.0 per cent of aluminum. When thealuminum-and silicon are used in conjunction I Prefer to use a total ofabout 5.0 per cent of aluminum and silicon combined-for instance about4.0 per cent aluminum and 1.0 per cent silicon;

Manganese alone may be added to magnesiumlead alloysin *amountsbetween0.1 per cent and 1.0 percent and has a stabilizing effect upon the alloyproperties in that it raises the hardness slightly, does not materiallydecrease the dormsion resistance, and adds to the matrix of the alioy ahardening element which expresses itself not only in an increase intensile strength but also surface hardness. An alloy of this naturecontaining about 8.0 per cent of lead and 0.85 per cent of manganeselost only 6 per cent of its original strength after 80 hours alternateimmersion in a 3 per cent aqueous solution of sodium chloride and in thesolution heat treated condition lost only 7 per cent of its strength inthe alternate immersion treatment. A magnesium alloy containing about10.37 per cent of lead had lost only about 10 per cent of its strengthat the expiration of this period as compared with certain othercommercial alloys, such as, for instance, the well known magnesium alloycontaining about 7 per .cent of aluminum and 0.4 per cent of manganesewhich, at the end of 40 hours of alternate immersion, had lost about percent of its strength.

Very favorable alloys can be compounded by using as a base an alloy ofmagnesium, lead and aluminum and making additions thereto of at leastone of the class of metals tin, manganese or zinc. The lead can be usedin amounts from about 0.5 per cent to about 22.0 per cent, the aluminumfrom about 1.0 per cent to about 15.0 per cent, the tin from about 1.0per cent to about 15.0

. per cent, the manganese from about 0.1 per cent to about 1.0 per cent,and the zinc from about 1.0 per cent to about 10.0 per cent. A sand castalloy within this range had, in the as cast condition, a tensilestrength of 27,500 pounds per square inch and an elongation of 5.7 percent in 2 inches. After a thermal treatment of 16 hours at 315centigrade, the alloy had a tensile strength of 29,640 pounds per squareinch and an elongation of 6.0 per cent in 2 inches. Some of theheattreated specimens were then given an alternate immersion treatment for40 hours and after the treatment the specimens had a tensile strength of28,413 pounds per square inch and an elongation of5l8 per cent in 2inches, this alloy containing 5.0 per cent of aluminum, 5.0 per cent oflead, 0.4 per cent of manganese and 2.0 per cent of zinc. The loss instrength on the corrosion treatment is observed to be less than 5 percent as compared to about 60 'per cent with the commercialmagnesium-aluminum-manganese alloy disclosed hereinbefore which containsabout 7 per cent of aluminum and 0.4 per cent of manganese.

As preferred compositions for alloys of this nature a I advise (1) 7.0percent of lead, 7.0 per cent of aluminum, 2.0 per cent tin, balancemagnesium; (2) 7.0 percent-lead, 7.0 per cent aluminum. 2.0 per centtin, 0.5 per cent manganese, balance magnesium; ,(3) 7.0 per cent lead,7.0 per cent aluminum, 2.0 per cent tin, 2.0 per cent zinc, balancemagnesium.

Two alloy compositions within this range which I have used to advantageare as follows: A mag-v with the addition of about 7 per cent of lead toan alloy containing 7 per cent of aluminum and 1 per cent of manganese,the loss of strength after 4/ the alternate immersion test was onlyabout 30 per cent, as compared with about 60 per cent of the same alloywithout lead.

Alloys of magnesium with lead, aluminum, and

manganese have been disclosed hereinabove. I havediscovered that if to abase alloy of magnesium-lead-aluminum-manganese I add one or more of theclass of metals calcium or cadmium, the resulting alloys becomeconsiderably more susceptible to variation of properties by thermaltreatments and their hardness can be markedly increased by artificialaging after thermal solution treatments. In these alloys the leadcontent should range from about 0.5 per cent to about 22.0 per cent, thealuminum from about 1.0 per cent to about 15.0 'per cent, and themanganese from about 0.1 per cent to about 1.0 per cent. To theseelements as a common base I add the elements cal-, cium, or cadmium,singly or in combination, the calcium in amounts from about 0.1 per centto about 2.0 per cent, the cadmium from about 1.0 per cent to about 10.0per cent. As an example of an alloy of this nature, a sand cast specimenof a magnesium-base alloy containing about 10.0

and this hardness was raised toabout 84 by an additional agingtreatmentof 20 hours at about 175 centigrade, the tensile strengthincreasing slightly to about 37,000 pounds per square inch; Similarly a.magnesium-base alloy containing about 5.0 per cent of lead, 7.0 percentof alumi-, num, 10.0 per cent of cadmium, and 0.4 per cent of manganesehad in the sand cast condition a tensile strength of about 24,000 poundsper square inch. Aftera thermal treatment of 21 hours at about 430centigrade the alloy had 'a tensile/ strength of about 35,000 pounds persquare inch. An additional aging treatment raised the Brinell hardnessof the-alloy from about 61 to about 79.

Similarly, a magnesium-base alloy containing about 5.0 per cent of lead,10.0 per cent of cadmium, 7.0 per cent of aluminum, 1.0 per cent of;

manganese, and 0.25 percent of calcium had in the sand cast condition atensile strength of about 24,290 pounds per square inch. Aftera thermaltreatment of 20 hours at about 430 centigrade this alloy had a tensilestrength of about 33,200 pounds per square inch. After an additionalthermal treatment of about 20 hours at'about 150 centigrade the strengthincreased to about 35,600 pounds per square inch and the Brinellhardness from about 47 to about 66.

Another magnesium-base alloy" containing,-

about 10.0 per cent of lead, 7.0 per cent of aluminum, 5.0 per centofcadmium, 0.4 per cent of manganese, and 0.1 per cent of calcium, hadin the sand cast condition a tensile strength of about 23,210 pounds persquare inch. 'After a thermal solution treatment of 21 hours at about430 centigrade the alloy had a tensile strength of about 36,030 poundsper square inch; the Brinell hardness was about 61. After an additionalaging treatment of about 20 hours at about 175 centigrade its tensilestrength was about 37,010 pounds per square inch and its Brinellhardness about 84. As. a desirable alloy of this nature I advise 7.0 percent lead, 7.0 per cent aluminum and, 0.4 per cent manganese. If morethe yield point of these alloys.

15.0 per cent.

- of the aluminum.

than one of the elements calcium or cadmium are present simultaneously,the total should not exceed about 10.0 per cent for preferred purposes.The addition of zinc in amounts from about 1.0 per cent to about 10.0per cent to magnesium- 5 lead alloys containing aluminum and silicon incombination decreases the linear shrinkage, thus favorably afi'ectingthe casting. properties, and also increases the corrosion resistance andraises In alloys of this type the lead should rangefrom 0.5 per cent tog 22.0 per cent, the aluminum from 1.0 per cent to 15.0 percent, and the'silicon from 0.1 per cent to 2.0 per cent, but the total amount ofaluminum and silicon should preferably not exceed A useful alloy of thisnature is a magnesiumbase alloy containingabout 10.0 per cent lead, 8.0percent aluminum "and 3.25 per cent zinc. Another useful composition isattained by substi- 20 tuting about 1.0 per cent silicon for part" orall An alloy'similarly improved in casting propv erties, although not tosuch a decided extent, is onecontaining, from about 0.5 per cent to 22.025

per cent of lead, from about 1.0 percent to about 10.0 per cent of zinc,and from about 0.1 per cent. "to about 2.0 per cent of silicon. Afavorable alloy within this range is a magnesium-base alloy consistingof about 10.0 per cent of lead, about 3.25 per cent of zinc, and about1.0 per cent of oxidizable metals.v The alloys, especially the .40

magnesium-lead binary alloys, may be extruded over the entire disclosedcomposition range, but other types of mechanical deformation such asrolling or forging should be carried'on with due regard for the factthat as the percentage of total added alloying elements increases, thenecessity for precaution/in working the alloy also increases. v

It-is my object to retain, as far as possible, the advantages of the useof magnesium base, such 50 as .low specific gravity, while securing inaddition the hereinabove disclosed benefits accruing from the additionsof the other alloying elements herein outlined. Accordingly, where inthe appended claims the term magnesium-base alloy is used, it refersto-an alloy containing more than approximately 50 per cent of'magnesium.

This application is a division of my copending application Serial No.692,135, filed October 4, 1933. I claim: g 1. A magnesium-base alloycontaining from about 0.5 to 22.0 per cent of lead,from about 1.0 to15.0 per cent of aluminum, and from about 1.0 to 10.0 per cent of zinc,the balance being magnesium.

nor E. Pr me.

